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Writer's pictureOzark DesignWorks

Design for CNC Machining: Part 1 - Overall Dimensions as Related to Common Stock Sizes

Updated: Feb 4, 2022

I've put together a short series that includes some best practices for engineering design for CNC machining that can translate to considerable time and cost savings on your next project.



Part 1: Overall Dimensions as Related to Common Stock Sizes


With CNC machining, designing your parts to nominal sizes like 0.5”, 1”, 2.5”

etc will actually increase material cost, run times, and waste.


Best Practice #1: Design your parts to be at minimum 0.12” thinner than the intended material raw stock size.


If you design your part to be, say 1” thick, your machinist may actually machine it from 1.5” thick material. A good rule of thumb is to design it to be 0.12-0.2” thinner than a common stock size (this is applicable to aluminum and plastics, steel stock sizes/tolerances can vary).


Best Practice #2: Design your parts to be 0.1” narrower than the intended material raw stock size.


If you design your part to be 4.0” wide, your machinist may have to buy 5” material and machine 0.5” off of both sides to get the final dimension to 4”. Designing it to be 3.9” wide would save considerable time and money.


Best Practice Example: Engineer designed part to be 0.85” x 2.9” x 3.47”.

Therefore, the machinist will select 1” x 3” extrusion and saw it to roughly 3.6”.








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